Three out-pouchings of the wall of the aortic root corresponding with the three leaflets of the aortic valve has been described by the Italian anatomist, Antonio Valsalva, in the fifteenth century. Animal and human physiologic studies indicate that these out-pouchings, i.e. the sinuses of Valsalva, may have favorable influence upon the function of the aortic valve. Studies have been conducted, both in ancient and modern times, which show that when the heart ejects blood, flow recoils at the edges of the aortic valve and exerts some degree of pressure on the lateral walls of the membranous aortic valve. As a result of this process the aortic valve begins to close before the cardiac contraction terminates and the disappearance of systolic gradient between the left ventricle and the aorta causes only the completion of closure of the aortic valve but not the initiation of the same.
Aortic valve prostheses (with or without an artificial aortic valve inside) uniformly disregard this physiologic phenomenon and aortic prostheses manufactured from sympatic tubes such as Dacron, of woven or knitted variety, which are made of "straight" tubes of constant diameters throughout, without such "out-pouchings," disregard the physiological principle of normal aortic valve function.